Measured and modelled tritium concentrations in freshwater Barnes mussels (Elliptio complanata) exposed to an abrupt increase in ambient tritium levels |
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Authors: | Yankovich T L Kim S B Baumgärtner F Galeriu D Melintescu A Miyamoto K Saito M Siclet F Davis P |
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Institution: | a AREVA Resources Canada, Safety, Health, Environment and Quality, P.O. Box 9204, 817-45th Street West, Saskatoon, Saskatchewan S7K 3X5, Canada b Atomic Energy of Canada Limited (AECL), Canada c Technical University Munich, Institute of Radiochemistry, Germany d “Horia Hulubei” National Institute for Physics and Nuclear Engineering (NIPNE), Romania e National Institute of Radiological Sciences (NIRS), Japan f Kyoto University Safety Reassurance Academy (SRA), Japan g Electricité de France (EDF), France |
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Abstract: | To improve understanding of environmental tritium behaviour, the International Atomic Energy Agency (IAEA) included a Tritium and C-14 Working Group (WG) in its EMRAS (Environmental Modelling for Radiation Safety) program. One scenario considered by the WG involved the prediction of time-dependent tritium concentrations in freshwater mussels that were subjected to an abrupt increase in ambient tritium levels. The experimental data used in the scenario were obtained from a study in which freshwater Barnes mussels (Elliptio complanata) were transplanted from an area with background tritium concentrations to a small Canadian Shield lake that contains elevated tritium. The mussels were then sampled over 88 days, and concentrations of free-water tritium (HTO) and organically-bound tritium (OBT) were measured in the soft tissues to follow the build-up of tritium in the mussels over time.The HTO concentration in the mussels reached steady state with the concentration in lake water within one or two hours. Most models predicted a longer time (up to a few days) to equilibrium. All models under-predicted the OBT concentration in the mussels one hour after transplantation, but over-predicted the rate of OBT formation over the next 24 h. Subsequent dynamics were not well modelled, although all participants predicted OBT concentrations that were within a factor of three of the observation at the end of the study period. The concentration at the final time point was over-predicted by all but one of the models. The relatively low observed concentration at this time was likely due to the loss of OBT by mussels during reproduction. |
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Keywords: | Organically-bound tritium OBT HTO Freshwater mussels Model comparison Dynamic |
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